The proper sequence of events in bone repair is

A. hyaluronic acid + proteoglycan monomers: Hyaluronic acid forms the central stalk (handle of the "toilet brush"), and proteoglycan monomers attach along its length, forming a large aggregate that traps water and gives ground substance its gel-like consistency.

B. reticular fibers + collagen fibers: These are structural protein fibers in connective tissue but are not components of proteoglycan aggregates.

C. chondroblasts and chondroclasts: These are cartilage cells involved in formation (chondroblasts) and resorption (chondroclasts) but not part of the ground substance's molecular structure.

D. collagen fibers + fibroblasts: Collagen fibers are structural; fibroblasts produce extracellular matrix components, but neither directly forms the proteoglycan aggregate.

A. hemidesmosomes: These anchor epithelial cells to the basement membrane, not for communication.

B. desmosomes: Desmosomes are responsible for mechanical adhesion between cells, providing strength but not facilitating communication.

C. gap junctions: These allow ions and small molecules to pass directly from one cell to another, enabling rapid cell-to-cell communication, especially in cardiac and smooth muscle.

D. tight junctions: These seal adjacent cells together to prevent leakage of substances between them, rather than enabling communication.